1. Field of the Invention
The present invention relates to a technical field of a signal delay apparatus, a leakage signal removing apparatus and an information processing apparatus. More specifically, the present invention relates to a technical field of a signal delay apparatus for controlling delay amounts of detected signals, which are obtained from a plurality of tracks formed on a recording medium, respectively, a leakage signal removing apparatus including the forgoing signal delay apparatus for removing a leakage signal caused by the detected signals of other trucks from any detected signal and an information processing apparatus including the leakage signal removing apparatus.
2. Description of the Related Art
Conventionally, in the case that the information is detected from the truck formed on the recording medium such as an optical disk or the like, an optical beam is irradiated to this truck and this information is detected on the basis of the reflected light of this optical beam from the track.
On one hand, in recent years, narrowing of truck pitch (namely, narrowing of spacing between the trucks, which are adjacently formed) in the trucks on the recording medium is noticeable at the request of improvement of the recording density. However, in this case, if the optical beam is irradiated to the truck, in which the information to be detected is recorded, a portion of a light spot formed by that optical beam on the recording medium is also irradiated on the truck adjoining the truck to be irradiated (namely, the truck which should not be originally irradiated by the optical beam). As a result, there was a case such that the information recorded in that adjoining truck was leaked in its reflection light as so-called cross talk (a leakage signal).
Therefore, conventionally, the above optical beam is divided into three on a flat surface by using a diffraction grating or the like. Then, a central one of them (hereinafter, referred to as a main beam) is irradiated toward the truck to be originally irradiated and other two beams (hereinafter, referred to as a sub beam, respectively) are irradiated to the two trucks adjoining the both sides of the truck to be originally irradiated, respectively. After that, two detected signals to be obtained from the reflection light of the sub beam are subtracted from the detected signals obtained from the reflection light of the main beam, so that the above described cross talk component, which is included in the detected signal obtained from the reflection light of the main beam, is deleted.
In the above case, according to the conventional cross talk deleting system, the main beam and two sub beams are generated by the diffraction grating or the like, so that a line connecting an irradiation center point of respective beams on the recording medium was not orthogonal to a moving direction of respective trucks.
Therefore, according to the conventional leakage signal removing system, the detected signals obtained from the reflection light of one of the sub beams and the detected signals obtained from the reflection light of the main beam are delayed by fixed times, which are different each other. Then, after orthogonalizing the line connecting the irradiation center points of respective beams and the moving direction of respective trucks for processing the signals (i.e., apparently), the two detected signals obtained from the reflection light of the sub beam are subtracted from the detected signals obtained from the reflection light of the main beam, respectively, so as to remove the above described cross talk.
However, according to the above described tendency of narrowing of truck pitch, the spacing between the above main beam and respective sub beams is also apt to be narrowed. Therefore, it is necessary to fix the spacing more exactly and remove the cross talk. On the contrary, if the oscillation wavelength of the semiconductor laser serving as an ejection source of respective optical beams is changed because of alteration of an ambient temperature or the like, the separation condition by the diffraction grating is changed. As a result, the spacing between the main beam and the sub beams subjects to be changed.
In this case, if this spacing is changed, originally, it is necessary to change the delay amount of respective detected signals depending on the change of the spacing. However, as described above, conventionally, the delay amount is always fixed for respective detected signals, so that this involves a problem such that it is not possible to obtain an appropriate delay amount for orthgonalizing the line connecting the irradiation center point of respective beams and the moving direction of respective trucks for processing the signals in response to the oscillation wavelength of the optical beam.
Further, this problem leads to a problem such that it is not possible to appropriately remove the cross talk and the detected signal is generated as the noise by the cross talk remains in the detected signal in association with the information to be detected, so that the information by the use of this detected signal can not be accurately recorded or reproduced.
The present invention has been made taking the present problems Into consideration, an object of which is to provide a signal delay apparatus capable of calculating an accurate signal delay amount for removing the cross talk even in the case that the irradiation manner of the optical beam such as the beam spacing or the like is changed, a leakage signal removing apparatus capable of more accurately removing the cross talk and further, an information processing apparatus capable of accurately performing the information processing such as recording or playing or the like by the use of the detected signal, from which the cross talk is accurately removed.
The above object of the present invention can be achieved by a signal delay apparatus of the present invention for delaying at least one of a main detected signal, which is optically obtained from a main truck, in which the information to be detected is recorded, or a sub detected signal, which is optically obtained from a sub truck other than the main truck. The apparatus is provided with: a filter device for generating a leakage signal, which is mixed in the main detected signal in association with the information, which is recorded on the sub truck, on the basis of a filter coefficient; a coefficient setting device for generating the filter coefficient on the basis of the main detected signal, of which the leakage signal is removed, and the sub detected signal, and for outputting the generated filter coefficient to the filter device: a delay amount controlling device for controlling the delay amount in the delay of any one of the main detected signal and the sub detected signal on the basis of the change in the filter coefficient, which is generated in a predetermined time period; and a delay device for delaying any one of the main detected signal and the sub detected signal by the controlled delay amount.
According to the present invention, on the basis of the change of a plurality of filter coefficients, the delay amount of respective detected signals is controlled, so that, even if the irradiation manner of the optical beam to be irradiated to respective trucks is changed, it is possible to delay respective detected signals by accurately controlling the delay amount.
In one aspect of the present invention, the signal delay apparatus is provided with a plurality of filter devices for generating the plural leakage signals, which are mixed in the main detected signal, respectively, in association with the information, which are recorded on a plurality of and different sub trucks, respectively, on the basis of the filter coefficient. Further, the coefficient setting device generates the respective filter coefficients, respectively, on the basis of the main detected signal, of which the respective leakage signals are removed, respectively, and a plurality of sub detected signals in association with the respective sub trucks, and outputting generated filter coefficients to the corresponding filter device. Moreover, the delay amount controlling device controls the delay amount in the delay of any one of the main detected signal and the sub detected signal on the basis of the change in the respective filter coefficients, which are generated in the time period with respect to the plural sub trucks.
According to this aspect, on the basis of the change of a plurality of filter coefficients in association with a plurality of sub trucks, the delay amount of respective detected signals is controlled, so that, even if the irradiation manner of the optical beam to be irradiated to respective trucks is changed, it s possible to delay respective detected signals by more accurately controlling the delay amount.
In another aspect of the present invention, the filter device is a digital filter device for digitally detecting the leakage signal. Further, the digital filter device is further provided with: a difference calculating device for calculating the difference between a plurality of tap coefficients; and the delay amount controlling device controls the delay amount on the basis of the calculated difference.
According to this aspect, the delay amount of respective detected signals is controlled on the basis of the difference between a plurality of tap coefficients in a digital filter device, so that It is possible to accurately control the delay amount with a simple structure.
In further aspect of the present invention, the difference calculating device calculates the difference between the Nth (N is a natural numeral) tap coefficient and the xe2x88x92Nth tap coefficient. Further, the delay amount controlling device controls the delay amount on the basis of the calculated difference.
According to this aspect, on the basis of the difference between the tap coefficients, which are symmetrical to a time axis, the delay amount is controlled, so that it is possible to accurately control the delay amount.
In further aspect of the present invention, the difference calculating device is provided with: a first calculating device for calculating a first difference, which is a difference between the Nth (N is a natural numeral) tap coefficient and the xe2x88x92Nth tap coefficient; a second calculating device for calculating a second difference, which is a difference between the Mth (M is a natural numeral and M is not equal to N) tap coefficient and the xe2x88x92Mth tap coefficient. Further, the delay amount controlling device controls the delay amount on the basis of sum of the first difference and the second difference.
According to this aspect, on the basis of a value obtained by adding two sets of the difference between the tap coefficients, which are symmetrical to a time axis, the delay amount is controlled, so that an error of the delay amount is detected in a wide range and it is possible to accurately control the delay amount.
In further aspect of the present invention, the difference calculating device calculates a difference between the Nth (N is a natural numeral) tap coefficient and the xe2x88x92Nth tap coefficient Further, the delay amount controlling device controls the delay amount on the basis of a value obtained by adding the calculated difference to a predetermined number of the tap coefficients.
According to this aspect, on the basis of a value obtained by adding a plurality of the differences between the tap coefficients, which are symmetrical to a time axis, the delay amount is controlled, so that it is possible to more accurately control the delay amount.
In further aspect of the present invention, the filter device is provided with a digital filter device for digitally detecting the leakage signal. Further, the delay amount controlling device is provided with: a multiplying device for multiplying respective tap coefficients in the digital filter device with a lapsed time from a predetermined standard time at a sample timing in association with the respective tap coefficients and for calculating the multiplied values, respectively; and an adding device for adding the multiplied values, which are calculated for the all tap coefficients, and for calculating added values. Moreover, the delay amount controlling device controls the delay amount on the basis of the calculated added value.
According to this aspect, on the basis of a value obtained by adding the value obtained by multiplying respective tap coefficients by a lapsed time from a standard time at a sampling timing in association with the respective tap coefficients to all tap coefficients, the delay amount is controlled, so that it is possible to more accurately control the delay amount.
In further aspect of the present invention, the digital filter device is provided with a FIR (Finite Impulse Response) filter.
According to this aspect, it is possible to more accurately control the delay amount.
The above object of the present invention can be achieved by a leakage signal removing apparatus of the present invention for removing a leakage signal from a main detected signal by using detected signals, which are delayed by a delaying device in a signal delay apparatus for delaying at least one of the main detected signal, which is optically obtained from a main truck, in which the information to be detected is recorded, or a sub detected signal, which is optically obtained from a sub truck other than the main truck. The signal delay apparatus is provided with: a filter device for generating a leakage signal, which is mixed in the main detected signal in association with the information, which is recorded on the sub truck, on the basis of a filter coefficient; a coefficient setting device for generating the filter coefficient on the basis of the main detected signal, of which the leakage signal is removed, and the sub detected signal, and for outputting the generated filter coefficient to the filter device; a delay amount controlling device for controlling the delay amount in the delay of any one of the main detected signal and the sub detected signal on the basis of the change in the filter coefficient, which is generated in a predetermined time period; and a delay device for delaying any one of the main detected signal and the sub detected signal by the controlled delay amount.
According to the present invention, it is possible to remove the leakage signal (cross talk) in the main detected signals.
The above object of the present invention can be achieved by a information processing apparatus of the present invention. The apparatus is provided with: (i) a leakage signal removing apparatus for removing a leakage signal from a main detected signal by using detected signals, which are delayed by a delaying device in a signal delay apparatus for delaying at least one of the main detected signal, which is optically obtained from a main truck, in which the information to be detected is recorded, or a sub detected signal, which is optically obtained from a sub truck other than the main truck, the signal delay apparatus is provided with: a filter device for generating a leakage signal, which is mixed in the main detected signal in association with the information, which is recorded on the sub truck, on the basis of a filter coefficient; a coefficient setting device for generating the filter coefficient on the basis of the main detected signal, of which the leakage signal is removed, and the sub detected signal and for outputting the generated filter coefficient to the filter device; a delay amount controlling device for controlling the delay amount in the delay of any one of the main detected signal and the sub detected signal on the basis of the change in the filter coefficient, which is generated in a predetermined time period; and a delay device for delaying any one of the main detected signal and the sub detected signal by the controlled delay amount, and (ii) a processing device for performing at least one of recording the information in the main truck on the basis of the main detected signal, of which the leakage signal is removed, or playing the information.
Therefore, it is possible to accurately perform any one of recording or playing by the used of the main detected signals, from which the leakage signals are accurately removed.